| 扬子板块黔中地区绿豆岩锂富集机制研究 |
| 投稿时间：2025-06-03 修订日期：2025-07-12 点此下载全文 |
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| 基金项目:国家重点研发计划（编号：2021YFC2901905）, 战略新兴产业矿产地质调查（KD-[2025]-XZ-061）, 战略性矿产成矿理论和找矿技术贵州省科技创新领军人才工作站（KXJZ[2024]016） |
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| 中文摘要:绿豆岩作为扬子板块早-中三叠世(T1-T2)海陆过渡期的关键标志层，广泛分布于扬子台地被动大陆边缘萎缩阶段的潮坪-潟湖相地层中(如嘉陵江组、雷口坡组)，其层位稳定且具有独特的矿物组合与地球化学特征，对重建印支期构造-沉积演化及Li资源勘探具有重要意义。近年来，随着战略性矿产Li需求的激增，绿豆岩因富锂(127~800×10-6)的特性成为沉积型Li矿的重要研究对象。本研究以扬子板块西南缘黔中地区为研究对象，运用显微镜鉴定、X射线衍射、扫描电镜与能谱分析等方法，揭示其成因机制。通过对绿豆岩的地球化学指标分析发现，长英质火山喷发提供了火山灰初始产物，在浅海-半咸水环境火山灰迅速蚀变为蒙脱石，通过蒙脱石层间吸附Li形成初始富集。埋藏阶段深部热液携带Li向上迁移，引发蒙脱石向伊利石转化。此过程释放层间水中的Li，并整合进入伊利石晶体中。绿豆岩中Li的主要以类质同象/吸附态的形式赋存于蒙脱石、伊利石及伊利/蒙混层中，随着伊利石含量的增加，Li含量同步增加，其富集机制与黏土矿物的形成过程和深部富Li流体息息相关。半局限构造盆地内蒸发浓缩与埋藏封闭系统共同驱动Li的持续富集，形成“火山灰蚀变-流体活化-矿物转化”多阶段动态模式，其成矿效率受温度、盐度梯度及构造-沉积耦合(台缘礁滩阻隔、快速沉降封存)的联合调控。 |
| 中文关键词:绿豆岩 锂富集机制 赋存状态 扬子台地 |
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| Research on the Lithium Enrichment Mechanism of Green bean rocks in the Central Guizhou Region of the Yangtze Plate |
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| Abstract:Green Bean Rocks(GBRs), as a key marker layer of the Early to Middle Triassic (T1-T2) sea-land transition period of the Yangtze Plate, is widely distributed in the tidal flat - lagoon-facies strata (such as the Jialingjiang Formation and the Leikoupo Formation) during the passive continental margin atrophy stage of the Yangtze Platform. Its strata are stable and have unique mineral assemblages and geochemical characteristics. It is of great significance for the reconstruction of the tectonic-sedimentary evolution of the Indosinian period and the exploration of Li resources. In recent years, with the sharp increase in the demand for strategic minerals, GBRs has become an important carrier of sedimentary Li ores due to its lithium-rich (127-800×10-6) characteristics. This study takes the central Guizhou region on the southwestern margin of the Yangtze Plate as the research object. Through systematic sampling and the application of methods such as microscopic identification, X-ray diffraction, scanning electron microscopy and energy spectrum analysis, its genetic mechanism is revealed. Through the analysis of geochemical indicators of GBRs, it was found that the eruption of feldspar volcanoes provided the initial products of volcanic ash. In the shallow marine-brackish water environment, volcanic ash rapidly eroded into montmorillonite, and the initial enrichment was formed through the interlayer adsorption of Li in montmorillonite. During the burial stage, the deep hydrothermal fluid carries Li upward, triggering the transformation of montmorillonite into illite. This process releases Li in the interlayer water and integrates it into the illite crystal. The Li in mung beans rock mainly exists in the form of isomorphic/adsorbed state in montmorillonite, illite and illite/montmorillonite layers. With the increase of illite content, the Li content increases simultaneously. Its enrichment mechanism is closely related to the formation process of clay minerals and deep Li-rich fluids. The evaporation concentration and burial closure systems in the semi-confined tectonic basin jointly drive the continuous enrichment of Li, forming a multi-stage dynamic model of "volcanic ash alteration - fluid activation - mineral transformation". Its mineralization efficiency is jointly regulated by the temperature and salinity gradient and the tectonic-sedimentary coupling (edge reef and beach isolation, rapid settlement and storage). |
| keywords:GBRs Lithium enrichment mechanism Occurrence state Yangzi Plateau |
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